How To Analyze Imagery

Measure Tools

measure_tools.png

You can measure the distance between two points, the area within a polygon or the bearing of a drawn line.

The measure tools are on the bottom right hand corner of the map, below the Draw an AOI button. If you float over this icon, you will see these available tools:

  • Note that when clicking on these tools to use them, the active tool that you are using turns teal. This will change depending on the active tool you are using at the time.

The first icon from the left (a compass icon) is the Measure Bearing tool, which allows you to measure the bearing between to points of your choice on the map. When you float your mouse over the map, you are prompted to Click on two points to calculate bearing.

Once you click on two points, the results are displayed on the map until you clear them (by clicking the trash bin icon). You can continue to create sets of two points and calculate their bearing, as needed.

  • Note: You can create multiple types of measures on the map. I.e. if you create a bearing measurement, and then choose to create an area measurement, both will continue to be visible on the map until you choose to clear them by using the trash bin Clear tool.

The second icon (a hashed polygon) is the Measure Area tool. When you float your mouse over the map, you will see a prompt: Click to create segments. Hold shift to draw free-hand. Click twice in same location to end. When you click through a few segments, and then double-click to end the polygon shape, it turns white and gives you a total area (in square kilometers). You can create as many measuring polygons as required. To clear, click the trash bin icon.

The last icon (a ruler icon) is the Measure Distance tool. You will be prompted on the map Click to create segments. Hold shift to draw free-hand. Click twice in the same location to end. After clicking through to create a few segments, you can double click to end the line measurements. The line will turn white, and a final distance will be displayed. You can create multiple measurements on the map - the clear it, click the trash bin icon.

Below is an example of using all three tools in the Measuring Tools set together. You can deactivate using any measuring tool by clicking on the icon a second time, which returns the icon to a gray color and deactivates the tool.

measure_results.png

Visualizations

visualization_tools.png

If you would like advanced tools to analyze the imagery beyond the Red-Blue-Green spectrum, you can use the visualization tools.

The visualization tools are located in the stack of tools on the right side of the map. When you click on the third button in the stack, you will see a menu of visualizations to choose from.

Note: If you are not currently viewing a Surface Reflectance Basemap, you will see a notification that prompts you to switch to a Surface Reflectance Basemap. If your organization has purchased access to multiple Surface Reflectance Basemaps, you will see a list view. If your organization has not purchased any Surface Reflectance Basemaps, you will have the option to view a demo Surface Reflectance Basemap. You can also contact sales to purchase a Surface Reflectance basemap.

The menu of visualizations includes:

  • RGB: Red Green Blue
  • CIR: Color-infrared
  • NDVI: Normalized Difference Vegetation Index You can click the “?” Icon at the left of the icons as a reminder for what the visualizations are.

If you click CIR, your basemap visualization will change automatically to be color infrared. If you click NDVI, you will have the option to select your color ramp. Click the edit tool in the upper right hand corner. Click the carrot indicator to view your options. Once you have selected a color ramp, you can save your preferences by clicking “Save”. Your imagery will then reflect the color ramp you chose.

Visualizations.gif

Compare Tab

compare_tab.png

You can compare sets of Planet imagery from different days, months, and quarters side by side.

In the left side panel, you will see the Compare tab next to the Browse tab. When you click the Compare tab, the map view changes, and you see a prompt to Drag & Drop Images to Compare.

Click and drag any image from the left pane, and release when on top of the map view. You can see the information box in the top center describes the image that has been added to the map view. Repeat again with a second image from the list in the left pane.

Now you can see two images have been added to the map view, and a slider bar is visible in the middle of the map view. The image on the left side of the slider icon corresponds with the tile description at the top left, and similarly for the image on the right side and the corresponding tile description on the top right.

By clicking on the slider icon and moving the mouse left or right, the map interface changes, and you can compare the two images that have been stacked one atop the other.

The icon in the top middle indicates that you can swap the imagery overlay (so that the bottom image becomes the top image).

To swap the image on the map view with a new image, simply click and drag a new image to the map view, and drop in the proper quadrant to replace the image you don't want to compare anymore.

When comparing imagery, there are two different tool icons in the bottom right stack - Slide and Fade.

Slide

This is the default option selected as you choose the Compare Tab. This controls the slider bar allowing you to view two images stacked atop each other.

compare_tools.png

Fade

If you choose the Fade option, you will see the top left image along with an Opacity slider bar at the bottom of the map view.

As you slide the Opacity bar to the right, the top image will Fade, and the features of the bottom image will start to become visible. In this case, the huge cloud from the bottom image is coming into view as the Opacity Bar is sliding to the right.

compare_opacity.png

Stories Timelapses

If you would like to compare multiple images, you can create a timelapse in the Stories applicable.

In the left side panel, next to the Compare tab, you will see the Stories Tab. When you click on this tab, you will see a pop-up with a link button to take you to the Planet Stories application. In Stories, you can make timelapses of multiple images. You can also publish your timelapses on Planet's website or on your own website or social media account.

stories_description.png